My invention comprises a transaxle assembly having a hydrokinetic torque converter and multiple ratio gearing for use with an internal combustion vehicle engine. In a preferred embodiment, the engine and the transaxle are mounted in a common powertrain package with the axis of the crankshaft of the engine in alignment with the axis of the hydrokinetic torque converter. The multiple ratio planetary gearing is mounted on the output shaft axis, which is arranged in parallel disposition with respect to the converter axis.
The engine and the output shaft axis may be mounted transversely in the forward vehicle engine and transaxle compartment of a front wheel drive vehicle with forward traction wheels. I am aware of prior art teachings of transaxle and engine assemblies of this kind, one example being shown in U.S. Pat. 4,509,389, which shows four-speed planetary gearing arranged concentrically with respect to a power output shaft. The output shaft in turn is connected to the output gear element of planetary gearing through a final drive gear mechanism.
Clutches and brakes for the design of the '389 patent deliver driving torque from a power input sleeve shaft to the planetary gear elements. The turbine of the hydrokinetic torque converter drives a drive sprocket mounted on the axis of the converter. A driven sprocket mounted on the axis of the output shaft is connected through a drive chain to the drive sprocket.
The gear elements of the design of the '389 patent are capable of establishing four forward driving speed ratios and a single reverse speed ratio. Another prior art four-speed ratio transaxle is shown in prior art U.S. Pat. No. 4,607,541.
Various attempts have been made to convert a basic four-speed ratio transaxle of the kind described above into a transmission capable of establishing five forward driving ratios. One example of such an attempt to increase the number of driving ratios is seen in U.S. Pat. No. 4,056,988 where an overdrive gear unit is shown in combination with a dedicated clutch and brake for overdrive operation. The clutch and brake are seen at 3 in FIG. 2 of the '988 patent. In that design, the overdrive gear is used to increase the number of ratios from three to four, but it requires the addition of a separate overdrive gear unit which adds to the complexity of the design and increases cost of manufacture and assembly. It also adds to the space requirements.
An example of an attempt to modify a four-speed in-line transmission to obtain a five-speed ratio transmission is seen in Ward's Engine Update Magazine, Page 6, published July 15, 1989. That publication describes an overdrive gear unit mounted at the output shaft end of an in-line transmission within the transmission extension housing. This requires an increase in the overall length of the transmission assembly and adds to the weight and cost.
Another example of a multiple ratio in-line transmission adapted for an overdrive ratio to complement basic three-speed ratio gearing is seen in U.S. Pat. No. 3,339,431. The added gear ratio of the design of the '431 patent is obtained by using an auxiliary planetary unit between the converter and the gearing. Like the previously described overdrive in-line transmission, the transmission of the '431 patent lacks economy of space because of the added axial dimension made necessary by the overdrive gearing.